Verified answer

Porcupine will sometimes chew on trees, its a habit they have, getting them out of a tree most likely leave them be a bit an they will get them selves down

I dont think that porcupines could do real damage to a tree because they lack big and strong enough teeth, although maybe they could mess with a sapling(baby tree). And about getting one out of a tree i think it would be the same idea as a cat; you never see cat skeletons in trees because when the cat gets hungry enough, it will get itself down.

Porcupines will eat anything that has any salt on it. Your car probably still has road salt on it, Do something before the porcupine discovers that nice salty brake line.

Try a live trap, such as a Hav-A-Hart, You can bait it with salt or a carrot.

Depends on how you define destructive to. Porcupines can be dangerous though